Descriptive grammarians and typologists often encounter unusual constructions or unfamiliar variants of otherwise familiar construction types. Many of these phenomena are puzzling from the perspective of linguistic theories: they neither predict these "anomalies" nor, arguably, provide the tools to insightfully describe them. In this talk we will analyze an unusual and underanalyzed type of relative clause found in many related and unrelated languages of Eurasia. We will examine a fragment of Tundra Nenets (Samoyedic) grammar in order to demonstrate that an understanding of this relative clause type benefits from exploring the (type of) grammar system in which it occurs: this permits the identification of a (set of) independent constructions that motivate its existence. We will argue that this relative clause type is probabilistically potentiated in languages which contain this recurrent set of independent constructions. This systemic explanation, correlatively, predicts where such relatives are unlikely to occur. In general, we will argue that the resulting insights into grammar organization illustrate the usefulness of a construction-theoretic syntax and morphology, informed by ideas and models from the developmental sciences for the understanding of complex adaptive phenomena such as the morphosyntax of natural language. Though the formal model of this proposal is developed in a modified variant of Head Driven Phrase Structure Grammar, no prior knowledge of this framework is necessary, since, in this talk, we will focus on basic properties of these constructions and standard linguistic arguments for assumptions concerning their hypothesized morphosyntactic status.